Digital contents have a superior quality to conventional analog contents and are conveniently manipulated. However, the digital contents can be copied by unlimited times, increasing the possibility and range of copyright infringement. In particular, the copyright infringement is severe when digital broadcast provides easily copied digital contents to a great number of subscribers. Accordingly, as digital content protection gets important with the development of a digital industry, various types of Digital Rights Management (DRM) schemes have been developed.
To solve the above-described problem, a conventional digital content protection/management system transmits digital contents in the entirely or partially encoded form, and a digital content execution device decodes the encoded contents using a stored security key from an external server and reproduces the contents.
However, the subscriber management based on the security key on the conventional digital content protection/management system was limited only to a method of providing an authority of executing digital contents to each subscriber or a method of providing the authority to each content execution device.
This does not consider that each subscriber has various digital content devices and each member of one home wants to enjoy digital contents together. Accordingly, the conventional digital content protection/management system makes the use of the digital content inconvenient and obstructs activation of a digital content providing industry.